Knobbly anemones are visually very variable. They can be white, maroon, pink, red, blue, purple or orange. Their central column is lined with a series of small, usually purple, knobs that are small and more darkly coloured than the rest of the body. These knobs are not sticky, and sand and debris do not stick to the column of knobbly anemones.
They inhabit sand-free rockpools and rocky reefs where they often stick to filter-feeding invertebrates such as redbait or mussels.
They are found on the southern African coast from Namibia to KwaZulu-Natal.